This invention relates generally to the field of weighing systems and more particularly to systems that weigh streams of fine powdered particles.
It is known that the flow rate and mass of a stream of moving material such as a fluid or stream of particles can be very accurately measured using a flowmeter such as is disclosed in my prior U.S. Pat. No. 5,230,251 which is incorporated herein by reference. The aforementioned patent discloses a curved guide which is mounted for pivotal movement along which the fluid flows. The system generates an output signal which is proportional to the flow rate (or mass).
While the foregoing system works extremely well with materials that flow easily, it is a well known problem in the art that very fine powers normally do not flow smoothly enough to be measured by devices such as described above. Very fine particles (less than about 100 microns in diameter) have microscopic spurs on their surface and as the particle mass decreases, the surface area increases. When the spurs grapple each other clumping occurs and the flow stream becomes intermittent or is interrupted altogether.
In view of the foregoing, it would be of commercial value to provide a small particle flowmeter which would make the mass/flow rate thereof accurately measurable.
It is accordingly an object of present invention to provide an improved flowmeter.
Another object of the present invention is to provide a flowmeter through which fine particles flow.
Yet another object of the present invention is to provide a fine particle flowmeter which is reliable.
Still another object of the present invention is to provide a fine particle flowmeter that has a high degree of accuracy.
A still further object of the present invention is to provide a fine particle flowmeter which can be used both as a flowmeter and as a scale.
To accomplish the foregoing objects, there is provided an apparatus for measuring the flow rate of a stream of material composed of fine particles characterized by the ability to maintain an even flow of the material and to accurately measure the flow of the moving stream. The apparatus comprises an elongate guide means for guiding the stream of material along a predetermined path. The guide means includes an entry end and an exit end and is mounted for pivotal movement about a pivot point. In certain embodiments, the pivot point is located so that a line drawn through the pivot point and the guide is at right angles to the average centrifugal force component of the stream of material and further wherein the line is parallel to the average friction force component of the stream of material on the guide means. In addition, the pivot point is located outside and remote from the stream of material to produce an electrical output signal that is free of signals induced by friction and is an accurate representation of the flow rate of the stream of material. In addition, a transducer is operatively associated with the guide for converting the force exerted by the stream of material on the guide into an electrical signal representative thereof. Also provided is a vibration source for vibrating the guide to keep the particle stream moving and wherein the plane of vibration is perpendicular to the plane of measurement.